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A/C Condensation Drainage Verification

Hello all,

Our home has a floor ventilation system and we recently discovered water in the vents. It just so happens that the water pools under the A/C coils/furnace unit where it blows the cooled/heated air into the vents. One thought was that this water could be condensation running off the A/C coils and into the vents. I looked into the coil drainage pipe which drains directly into our sewage system and water is running through that pipe when the A/C unit is working, so I would think the condensation is being properly removed from the unit/house but I am not sure as I am not familiar with the construction of the coils and the pan under them.

Is it possible that some of the condensation could be running into the floor vents while some properly drains, or would you expect that condensation is properly removed if it is flowing out the unit drain pipe?

The company that installed the unit 2 years ago came out and checked and claims it is draining properly and the water is not from the unit, but I am just wondering if they were covering their rear.

There is no real way, absent observing the drain pan itself, to verify all the water from the condensate drain pan is exiting via the drain pipe. It's possible there could be a small joint leak, crack or other anomaly of the drain pipe, allowing a small percentage of the condensate to escape. On the other hand, I've seen all manner of plenums and near ducts 'sweating' due to low airflow and cold air temps within. So absent being on scene to help make a determination, I can't offer much. I'm suspicious that your HVAC company couldn't determine the root cause. Perhaps you should invite them back out, as a callback to further diagnose the problem. Unless you've got high ground water and subsequent natural water infiltrating from the basement or crawl space, I'd say the chances are 99% that it's coming from the AC system, just not necessarily the condensate drain.

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If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

Water in vents

Thank you for the info. We potentially have water backing up under the house from the front yard (our front yard slopes down towards our house, but not likely as I have already built the dirt up around the front of the house to drain water away for 4 - 5 ft where it can run around the side of the house). However, it is hard to say for sure that is not the problem either. No basement -- just a concrete slab.

How difficult is it to get into the coil and drain pan on a down-flow unit? It appears that I have to take the furnace and fan unit off the top of the coil box, but I can't tell for sure and this is not my expertise.

This has potiential of creating a big indoor air quality problems. Standing water in ducts will grow mold throughout the supply ducts and high humidity throughout the home. Suggest a small sump near the standing water with a pump. Also to assure dry supply ducts, start with the fan in the "on" mode to assit drying out. If you have a reoccuring moisture problem, use the sump and a small whole house dehumidifier to keep the ducts dry when the a/c is not operting. If unable to keep the ducts dry, you must fill in the ducts and install above grade ducts.
This is a serious indoor air quality problem!
Regards TB